[NET]: Fix GSO problems in dev_hard_start_xmit()

Fix 2 problems in dev_hard_start_xmit():

1. nskb->next needs to link back to skb->next if hard_start_xmit()
returns non-zero.

2. Since the total number of GSO fragments may exceed MAX_SKB_FRAGS + 1,
it needs to stop transmitting if the netif_queue is stopped.

Signed-off-by: Michael Chan <mchan@broadcom.com>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/dev.c

@@ -1325,9 +1325,12 @@ int dev_hard_start_xmit(struct sk_buff *skb, struct net_device *dev)
 		nskb->next = NULL;
 		rc = dev->hard_start_xmit(nskb, dev);
 		if (unlikely(rc)) {
+			nskb->next = skb->next;
 			skb->next = nskb;
 			return rc;
 		}
+		if (unlikely(netif_queue_stopped(dev) && skb->next))
+			return NETDEV_TX_BUSY;
 	} while (skb->next);
 
 	skb->destructor = DEV_GSO_CB(skb)->destructor;